Sub-caliber conversion unit

ABSTRACT

A sub-caliber conversion unit adapted to be detachably secured to and firmly supported by the lower receiver group of a larger caliber pistol, wherein the slide in such conversion unit operates independently of the barrel, and means are provided to permit full travel of said slide.

finite totee etent 11 1 y 1 Nov, en, 1973 [5 SUB -CALHBEER CONVEIRSHQN lUNll'll 1,563,675 12 1925 Tansley 42 7 [76] Inventor: Robert W. Day ,75 l5 Stagecoach Ln., San AntOlllO, T 78227 Primary Examiner-Stephen C. Bentley [22] Filed: Mar. 26, 1973 ttorney-John C. Srahl [21] Appl. No.: 344,732

Related U3. Application Data [62] Division of Sel'. No. 167,208, July 29, 1971, Pat. No. [571 AESTRACT A sub-caliber conversion unit adapted to be detach- [52] US. (3] 42/7, 42/49 A, 42/50 ably secured to and firmly supported by the lower re- [51] Tm. m. M111: zfiloe ceiver g p of a larger caliber p wherein the [58] [Field of Search 42/6, 7, 49 R, 49 A, slide in such conversion unit operates independently 42/50 of the barrel, and means are provided to permit full travel of said slide.

[56] References Qifiecrii UNITED STATES PATENTS 6 Claims, l5 inn-owing; Figures PATENTED NOV 20 I975 sum 1 or 5 \N ms 3 m N% R NH QM m1 R PATENTEDnuv 20 ms 3772.812

. SHEET 2 [3F 3 FIG. 4

FIG. 9

PATENTED NOV 20 1975 SHEET 3 BF 3 FIG. I2

FIG. ll

FIG. [4

FIG. l3

SUB-CALIBER CONVERSION UNIT The subject application is a division of application Ser. No. 167,208, filed July 29, 1971, now U.S. Pat. No. 3,724,326.

BACKGROUND OF THE INVENTION The sub-caliber conversion unit of the subject invention coacts with the lower receiver group of a larger caliber pistol without modification or alteration thereto, and the sub-component parts thereof operate in their normal, intended manner. Such conversion unit is rapidly and easily secured to or removed from the lower receiver group. The barrel is supported along its longitudinal axis by said lower receiver group thereby eliminating the inaccuracies inherent in prior art conversion units. Means are provided whereby the recoil spring operates the slide independently of the barrel and allows full travel of said slide. A coacting subcaliber magazine insert, detachably secured in the magazine of the large caliber pistol, provides sub-caliber cartridges for such sub-caliber pistol.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sub-caliber conversion unit which is rapidly and easily installed on or removed from the lower receiver group of a larger caliber pistol, wherein no modification of or alteration to said lower receiver group is required.

Another object is the provision of such a sub-caliber conversion unit which is firmly supported at several cations along its longitudinal axis by the lower receiver group.

A still further object is the provision of such a subcaliber conversion unit wherein the slide operates independently of the barrel, and means are provided to permit full travel of said slide.

A further object is the provision of a sub-caliber conversion unit adaptable for use with the lower receiver group of a larger caliber pistol including a sub-caliber magazine insert detachably secured in the magazine of said larger caliber pistol.

A final object is to provide such a sub-caliber conversion unit adaptable for use with the lower receiver group of most larger caliber pistols, without modification, wherein the sub-components thereof operate in their normal, intended manner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view, partly broken away and partly in section, of the conversion unit of the subject invention, said conversion unit is detachably secured to the lower receiver group of a larger caliber pistol.

FIG. 2 is a vertical sectional view, transverse to the longitudinal axis, taken along the line 2-2 of FIG. I, looking in the direction of the arrows.

FIG. 3 is a vertical sectional view, transverse to the longitudinal axis, taken along the line 3-3 of FIG. 1, looking in the direction of the arrows.

FIG. 41 is a fragmentary, side'elevational view, partly broken away and partly in section, of the foremost and medial portions of sub-caliber conversion unit with a blade sight secured to the barrel housing, showing the slide secured in retracted position.

FIG. 5 is a fragmentary, vertical sectional view showing another means for securing the barrel housing to the foremost end of the receiver.

FIG. 6 is a fragmentary, plan view taken along the line 6--6 of FIG. 5, looking in the direction of the arrows.

FIG. '7 is a fragmentary, side elevational view, partly broken away and partly in section, showing still another means for securing the barrel housing to the foremost end of the receiver.

FIG. 8 is a vertical sectional view, transverse to the longitudinal axis, taken along the line 8-8 of FIG. 7, looking in the direction of the arrows.

FIG. 9 is a fragmentary, side elevational view, partly broken away and partly in section, showing another means for securing the rear portion of the barrel housing to the receiver.

FIG. It) is a vertical sectional view, transverse to the longitudinal axis, taken slightly rearwardly of the rear face of the barrel housing, looking in a forward direction.

FIG. 11 is a fragmentary, horizontal sectional view, showing another means for securing the rear portion of the barrel housing to the receiver.

FIG. 12 is a fragmentary, side elevational view showing still another means for securing the rear portion of the barrel housing to the receiver.

FIG. 13 is a side elevational view, partly broken away and partly in section, showing the magazine utilized in the larger caliber pistol with a sub-caliber magazine insert detachably secured therein, which insert accommodates ammunition for the sub-caliber pistol.

FIG. 14 is a side elevational view, partly broken away and partly in section, of the magazine insert.

FIG. 15 is a top plan view of FIG. 14 of the drawings.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. I of the drawings an embodiment of the sub-caliber conversion unit 20 of the blow back type which is adapted to coact with the lower receiver group 21 of a larger caliber pistol, such as the Government model Colt I5 caliber semi-automatic pistol or the like; alternatively, an automatic pistol may be constructed in accordance with the principles of the invention. Conversion unit 20, which has the general shape and dimensions of the corresponding parts of the larger caliber pistol, comprises barrel housing 22, barrel 23, breech block 24, reciprocable slide 25, and desirably a sub-caliber magazine insert 26, or separate sub-caliber magazine. Removal of cross pin 27 and slide stop 28 (see FIG. 4) of the larger caliber pistol permits the barrel and slide assembly to be removed from the receiver. The lower receiver group 211 to which conversion unit 20 is detachably secured by means of cross pin 27 and slide stop 28 comprises the frame, trigger mechanism, hammer, sear, springs, safeties, stocks, and magazine of the larger caliber pistol.

In the embodiment of FIG. ll of the drawings, barrel 23 of any desired sub-caliber is carried in barrel housing 22. Barrel 23 terminates rearwardly in an integrally formed, angularly downwardly extending cartridge loading ramp 29 which aids in guiding a cartridge C into the cartridge chamber. It is understood that the invention is not to be restricted solely to a barrel housing with a separate barrel insert but also covers a barrel housing which is rifled to any desired caliber and further includes an integrally formed cartridge loading ramp.

Longitudinally extending tubular section 30 is integrally formed on the foremost end of barrel housing 22 downwardly of barrel 23. Cylindrical plug 31, adapted to insert into the foremost end of bore 32 in section 30, may be adjusted in length and/or composition by the user to provide a desired barrel weight. Vertically extending female threads 33 in plug 31 accommodate set screw 34 the remote end of which abuts nylon insert 35 or the like carried in a communicating bore 36 in barrel housing 22. Insert 35 is adjusted to bear against the lower surface of barrel 23 by means of set screw 34 thereby securing plug 31 and also eliminating manufacturing clearances between the barrel housing and the barrel. A horizontally extending shoulder 37 (see FIG. 4) which lies in a plane slightly below the upper limit of bore 32 is provided in each side of the barrel housing, said shoulder 37 extends into the rear face of tubular section 30.

Barrel housing 22 terminates rearwardly in an integrally formed and downwardly depending lug 38; the rear face of the barrel housing, barrel and lug terminate in the same transverse, vertical plane. A transversely extending bore 39 in lug 38 accommodates cross pin 27 heretofore mentioned whereby the rear portion of the barrel is detachably secured to the receiver.

Breech block 24, of any desired material and preferably of suitably heat treated steel, is generally U-shaped in elevation, comprising base 40 with spaced, upstanding fore and aft portions 41-42, respectively. The breech block thus formed is detachably secured in the rearmost, upper portion of slide 25 by means of transversely extending pins 43-44 which are passed through bores in slide 25 and insert into aligned bores in portions 41-42, respectively. Longitudinally extending bore 45 passes through portion 41 of the breech block while coaxial bores 46-47 of progressively greater diameters are provided in aft portion 42. Firing pin 48 passes through bore 46 and terminates forwardly in a reduced diametral extension 49 which carries spring 50, said extension partially inserts into bore 45 and is adapted to strike cartridge C; the ends of spring 50 abut the rear surface of portion 41 and shoulder 51 of the firing pin maintaining the pin in normally retracted condition. Rearwardly, firing pin 48 terminates in transversely extending and spaced collars 52-53 which ride in bore 47 with pin 44 passing intermediate the said collars thereby retaining the firing pin in the breech block. A cartridge extractor 54, such as is wellknown in the art, is carried in breech block 24; the empty cartridge cases are ejected through port 55 by striking ejector 56 which may be provided on magazine insert 26, installed in conversion unit 20, or on lower receiver group 21.

It is to be understood that breech block 24 may be integrally formed with slide 25; in such modification of the invention pin 43 is not required and the rearmost pin 44 is utilized solely to retain firing pin 48 in the composite slide-breech block.

As best seen in FIGS. 4 and of the drawings, the lower surface of barrel housing 22 rearwardly of tubular section 30 is milled or otherwise removed to provide a generally horizontal flat 57 which extends along a plane slightly above the upper limit of bore 32 in tubular section 30, said flat also extends laterally of lug 38. The lower sides of barrel housing 22 corresponding to flat 57 are provided with shoulders 58 which parallel and are above the plane of flat 57; shoulders 58 terminate inwardly in vertically extending shoulders 59. The interior angle formed between the foremost end of shoulder 58 and the rear end of tubular section 30 is desirably radiused, indicated by reference numeral 60, and the exterior angle formed between the rearmost portion of shoulder 58 and the rear end of barrel housing 22 is also desirably radiused, indicated by numeral 61.

Still referring to FIG. 4 of the drawings, slide 25 further includes integrally formed and forwardly extending sides 62 which pass laterally of each shoulder 59 on the barrel housing with the upper edge of each side generally paralleling and spaced slightly downwardly of the respective shoulder 58; the lower edge of each side 62 lies in the plane of shoulder 37. Forwardly, an integrally formed cross member 63 joins the opposing sides; the upper surface 64 of said cross member is approximately medially the upper and lower edges of sides 62. The innermost surface of each side includes a longitudinally extending slot 65 which extends forwardly into cross member 63, forming recess 66 therein. Downwardly depending section 67, integrally formed with cross member 63, is generally U-shaped in transverse section and is adapted to slidably insert into the foremost end of the receiver; section 67 includes a longitudinally extending bore 68 which is coaxial with bore 32 in tubular section 30. The foremost ends of cross member 63 and section 67 are vertically aligned, and as viewed in FIG. 1 of the drawings, in loaded and cocked condition, such vertically aligned portions are spaced slightly rearwardly of the rear end of tubular section 30.

Counterbore 69 in the rear end of section 67 accommodates flange 70 of a forwardly extending, cupshaped retainer 71, said retainer includes axial bore 72 in the foremost end thereof. Elongated guide pin 73 which terminates rearwardly in head 74 carries recoil spring 75; the foremost end of said pin passes through bore 72 with the ends of spring 75 bearing against the inner surface of retainer 71 and head 74, respectively; the rearmost end of head 74 is placed against the face of lug 38. The recoil spring and guide thus formed are free-floating and self-aligning under all conditions. When slide 25 is in the retracted position, illustrated in FIG. 4 of the drawings, recoil spring 75 is compressed principally within retainer 71.

As heretofore mentioned, the foremost end 76 of receiver 77 is generally U-shaped in transverse section (see FIG. 8), permitting section 67 of slide 25 which inserts therein to move rearwardly until the rear end thereof abuts an integrally formed and transversely extending shoulder 78 in the receiver, said shoulder is positioned forwardly of bore 79 (see FIG. 10) which accommodates cross pin 27. Rearwardly of bore 79 the receiver 77 includes an integrally formed, transversely and vertically extending member 80. Longitudinally extending and spaced slide rails 81 begin in proximity to shoulder 78 and extend rearwardly approximately along the plane of flat 57.

The user inserts the foremost end of rails 81 of the receiver into the mating and rearwardly opening slots 65 in the slide and conversion unit 20 is pushed rearwardly. Lug 38 is adapted to pass intermediate slide rails 81 in a close fit and the upper surface of said slide rails bear against flats 57 laterally of lug 38. Simultaneously the foremost end of the receiver passes outwardly of section 67 of the slide; continued rearward movement of conversion unit causes tubular section 30 of the barrel housing to insert in a tight fit into the foremost end 76 of the receiver until stopped by the rear surface of lug 38 butting the foremost surface of member 80.

In the preferred embodiment of the invention, barrel housing 22 and lug 38 are preferably composed of a malleable material, such as aluminum. Bore 39 in lug 38 is slightly out of alignment with respect to bore 79 in the receiver; when cross pin 27 is driven into bore 79, and thence into bore 39, the lug 38 is pulled downwardly and rearwardly whereby Hats 57 laterally of lug 38 firmly seat upon the upper surface of slide rails 81 and the rear surface of lug 38 bears firmly against the foremost end of member 80 in the receiver.

The foremost end 76 of receiver 77 is secured to tu bular section 30 by means of clamp 82 detachably secured at one end to section 30 and adapted to pass downwardly of and support the foremost end of said receiver.

There is shown in FIGS. 5-6 of the drawings another embodiment of securing means for the foremost end of the receiver. More particularly, recess 83 in the lower surface of tubular section 30 accommodates one end of a spring clamp 84 detachably secured therein by means of screw 85 or other fastening means whereby spring tension is applied against the foremost end 76 of the receiver.

In the embodiment of FIGS. 7-8 of the drawings, the rearmost portions 86 of tubular section 30 extend substantially outwardly of the corresponding portions of the foremost end 76 of the receiver; a rearwardly opening, generally U-shaped recess 87 is provided therein into which the foremost end of the receiver inserts in a close fit. Set screw 88 or the like passes through section 86 and is adjusted to bear against end 76, additionally securing the same in recess 87.

Referring now to FIGS. 9-10 of the drawings, there is shown another means for securing the rear portion of the barrel housing 22 to the lower receiver group 21. More specifically, barrel housing 22 terminates rearwardly in a downwardly depending lug 89 the rear end of which is vertically aligned with the rear end of the barrel housing. A longitudinally extending slot 90 is provided in the bottom surface of the lug with a communicating, angularly upwardly extending slot 91 terminating rearwardly in the face of said lug. A longitudinally extending bore 92 which is slightly below the plane of flat 57 communicates rearwardly with slot 91. A transversely extending recess 93 in lug 89 opens downwardly and terminates upwardly in the approximate plane of slot 90. One end 941 of a spring is adapted to insert into bore 92; portion 95 of said spring lies in slot 91 and extends downwardly through slot 90; terminal portion 96 of said spring lies in slot 90 forwardly of recess 93 and extends angularly upward. It is to be understood that portions 95,96 of the spring partially restrict passage of cross pin 27 through recess 93. When pin 27 is driven into bore 79 in the receiver, the foremost end is stopped by said spring. An additional force causes pin 27 to ride over the lower portions 95,96 thereby exerting a downward and rearward spring tension on the barrel housing.

In the embodiment of FIG. 1 1 of the drawings, lug 97 includes a transversely extending, tapered bore 98 adapted to receive a mating, tapered pin 99; said pin is driven through bore 79 in the receiver, through tapered bore 98, and thence into aligned bore 79 in the opposite side of the receiver. Female threads 100 in the remote end of pin 99 accommodate screw 101 whereby slide stop 102 is detachably secured thereto.

Referring now to FIG. 12, barrel housing 22 includes an integrally formed, downwardly depending lug 103; transversely extending slot 104 which preferably opens downwardly communicates with an angularly upwardly and rearwardly extending slot 105. Drive pin 27 is first passed through aligned bores 79 in the receiver with the said pin passing through slot 104. A downward force applied to the rear portion of the barrel housing causes pin 27 to partially ride up inclined slot 105 securing the barrel housing to the receiver. To remove barrel housing 22 from the receiver, pin 27 must first be removed.

A downwardly opening recess 106 (see FIG. 4) is provided in the outer surface of side 62 adjacent the rear end of slide stop 28 whereby slide 25 may be locked to the rear. Conventional sights 107 are mounted upon the upper surface of the barrel housing 22 or slide 25.

There is shown in FIGS. 1345 of the drawings subcaliber magazine insert 26 which desirably inserts into a conventional magazine 108 of the larger caliber pistol. Magazine 108 is integrally formed comprising spaced sides 109-110, rounded front 111, back 112, base 113 and an internal, spring activated follower 114 or the like whereby cartridges are fed into the cartridge chamber in the barrel. A rectangularly shaped magazine catch slot 1 15 is provided in .a uniform, exact location in each such type magazine, normally in the upper, right-hand side 109 and which in some magazines at least partially extends into front 111. Magazine insert 26 comprises spaced sides 116-117, front 118 and back 119, which portions are adapted to pass inwardly of the corresponding members of the larger caliber magazine 108. Slot 120 (see FIG. 14) is provided in side 116, said slot terminates upwardly in perpendicularly extending slot 121 forming an outwardly extend ing lip 122 adapted to insert into the rearmost portion of magazine catch slot 115 in the larger caliber magazine 108. Bracket 123 is secured at any desired location on back 119 whereby insert 26 is positioned forwardly in magazine 108.

Follower 124 (see FIG. 15), carried in insert 26, is stopped upwardly by means of inturned lips 125-126 on the upper end of the respective sides. Ejector 56 heretofore mentioned preferably extends perpendicularly upward of lip 126. Downwardly depending lug 127 on follower 124 accommodates one end of spring 128; the lower end of said spring bears against a L- shaped floor 129 which is maintained in insert 26 by pin 130 bearing against the lower surface of the said plate and passing through aligned bores (not shown) in the lower portions of sides 116,117.

The user positions insert 26 upon follower 114 of magazine 108 and exerts a downward force thereon until lip 122 inserts into the rearmost portion of slot 115. To remove insert 26 from magazine 108, a pointed tool is inserted in slot 115 thereby depressing lip 122 at which time insert 26 is forceably ejected from the larger caliber magazine by the spring activated follower 1 M.

Sub-caliber magazine insert 26 may be loaded or unloaded either prior to or after insertion in magazine 108. It is to be understood that the invention is not to be restricted solely to the use of magazine catch slot 115 but a slot or other opening may also be provided on'any other selected part of the magazine to accommodate a coacting member, or other securing means may be provided on the larger caliber magazine and the coacting sub-caliber magazine insert carried therein.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. In combination with a magazine of a larger caliber firearm comprising spaced sides, front, back, base, spring activated follower, and a slot in a selected portion of said magazine,

a sub-caliber magazine insert adapted to be positioned in said larger caliber magazine comprising spaced sides, front, back, spring activated follower, and

means on said sub-caliber magazine insert adapted to engage a selected portion of said slot in said larger caliber firearm.

2. The invention of claim 1 wherein said slot is the magazine catch slot.

3. The invention of claim 2 wherein said means comprises a lip which partially inserts into the rearmost portion of said magazine catch slot.

4. The invention of claim 1 further including means on at least said back of said sub-caliber magazine insert to position said insert in the larger caliber magazine.

5. The invention of claim 1 wherein an ejector is integrally formed on at least one side of said sub-caliber magazine insert.

6. In combination with a magazine of a larger caliber firearm comprising spaced sides, front, back, base and spring activated follower,

a sub-caliber magazine adapted to insert in said larger caliber magazine comprising spaced sides, front, back and spring activated follower,

means on said sub-caliber magazine to position said sub-caliber magazine in said larger caliber magazine, and

means on said sub-caliber magazine adapted to secure said sub-caliber magazine in said larger caliber magazine. 

1. In combination with a magazine of a larger caliber firearm comprising spaced sides, front, back, base, spring activated follower, and a slot in a selected portion of said magazine, a sub-caliber magazine insert adapted to be positioned in said larger caliber magazine comprising spaced sides, front, back, spring activated follower, and means on said sub-caliber magazine insert adapted to engage a selected portion of said slot in said larger caliber firearm.
 2. The invention of claim 1 wherein said slot is the magazine catch slot.
 3. The invention of claim 2 wherein said means comprises a lip which partially inserts into the rearmost portion of said magazine catch slot.
 4. The invention of claim 1 further including means on at least said back of said sub-caliber magazine insert to position said insert in the larger caliber magazine.
 5. The invention of claim 1 wherein an ejector is integrally formed on at least one side of said sub-caliber magazine insert.
 6. In combination with a magazine of a larger caliber firearm comprising spaced sides, front, back, base and spring activated follower, a sub-caliber magazine adapted to insert in said larger caliber magazine comprising spaced sides, front, back and spring activated follower, means on said sub-caliber magazine to position said sub-caliber magazine in said larger caliber magazine, and means on said sub-caliber magazine adapted to secure said sub-caliber magazine in said larger caliber magazine. 